Discriminant function analysis of the occurrence risk of abnormal electrocardiogram in thyroidectomized...

The common form and risk factors of electrocardiogram (ECG) abnormality in thyroidectomized differentiated thyroid carcinoma (DTC) patients with short-term overt hypothyroidism were investigated and some discriminant formulas for forecasting the occurrence of abnormal ECG in this specific population were deduced in this study.

A total of 260 thyroidectomized DTC patients were retrospectively reviewed, 67 of whom had abnormal ECG and 193 normal ECG after short-term (3 weeks) levothyroxine (L-T4) withdrawal. One-way ANOVA, Spearman's rank correlation analysis and discriminant function analysis were performed using data from these DTC patients.

A flat or inverted T wave in inferior myocardial and left ventricular wall leads was the most common abnormal ECG finding in short-term overt hypothyroidism. Statistical analyses showed that age, interval, TSH-end (The serum hormothyrin level at the end of L-T4 withdrawal for 3 weeks), and TSH-vel (The average ascending velocity of serum hormothyrin level during L-T4 withdrawal for 3 weeks) were statistically significant and positively correlated with the occurrence of abnormal ECG. Meanwhile, TSH-vel showed the highest correlation coefficient (r = 0.358, p = 0.000). The formulas, especially deduced from age, interval and TSH-vel, could discriminate patients with abnormal ECG or not as high as 77.6 and 70.5%, respectively (resubstitution accuracy: 72.3%).

The thyroidectomized DTC patients undergoing short-term L-T4 withdrawal before their first radioiodine ablative therapy, who had one or more of the above-mentioned risk factors, are likely to show abnormal ECG findings. The formulas from discriminant function analysis may be helpful for predicting patients with abnormal ECG with short-term L-T4 withdrawal and allow appropriate medical intervention beforehand.